It is a serious waste to use disposable paper for writing or printing, and from the viewpoint of the protection of environment and the reuse of resources, it is particularly important for the cyclic utilization of papers. At present, there is much reusable water writing paper on market that displays color when contacting with water. However, such existing water writing paper is either consisted of a paper substrate, a carbon black layer and a white-sprinkled layer, or is directly consisted of a dark base paper and a white-sprinkled layer. For example, CN2628572Y discloses a reusable water writing paper. However, such water writing display is achieved on a physical change that the white-sprinkled layer becomes transparent upon contacting with water, and make the underneath carbon black layer or dark base paper visible. Most of the color of characters displayed by the water writing papers produced with this process is black, without a high contrast and resolution, and the applied field is limited to writing exercise and drawing. There is a great potential market to develop a kind of water writing paper that has various color choices, satisfies the requirements for both writing and printing at the same time, and can be reusable.
In addition, since an inkjet printer has several advantages, for example, the machine itself is cheaper than a laser printer; also it has lower amount of irradiation than a laser machine, zero ozone production, and the prints is brightness, or the like, it is always very favorite. However, the ink of an inkjet printer is easily rebarbative, on one hand, frequent replacement of the ink cartridge causes the increase in the subsequent costs; on the other hand, the consumer may also suffer to stains by the ink without a careful caution. From the viewpoint of environment protection, the frequent replacement of consumptive materials results in large amount of industrial wastes, and inappropriate treatment may further result in the contamination of water and soils. Furthermore, when one wants to print something, the ink of an inkjet printer may also block the nozzle due to the non-use for a long time. In order to solve the problems caused by the frequent replacement of ink cartridges or being stained by the ink, at present, some printer manufacturers use the way to connect a continuous ink supply system (CISS) to the printer. However, the problems such as the subsequent costs for re-injecting ink and the nozzle clogging caused by not being used frequently are not solved yet. If the subsequent costs for injecting ink can be decreased or even eliminated, the users of an inkjet printer will be greatly increased.
In order to satisfy the consumer's requirements for daily printing and for business printing, at the same time in view of the eternal theme of green environment protection, the inkless printing technique is proposed and attracts the attention at home and abroad. The key for the inkless printing technique is the paper adopted. Inkless does not mean that there is no ink to be used, but the ink is transferred onto the paper. Based on this kind of special ink-containing paper, in combination with a printing device capable of stimulating the ink-containing paper to change colors, inkless printing can be achieved.
Inkless printing device enables the realization of inkless printing. On one hand, it solves the problems such as the solid waste pollution caused by the frequent replacement of ink cartridges and the nozzle clogging. On the other hand, if the ink-containing color-changeable substrate can be reused, the dissipatation of paper may also be reduced. Because environment protection and energy saving are advocated more and more in this society, it is believed that, inkless printing which is cheap, performance stable, energy saving and environment protecting will be occurred in office or home gradually with the continuous development of the printing techniques and reusable erasing/writing materials. The application of inkless printing devices will also be more common.